This application claims priority to Korean Patent Application No. 2002-62573, filed on 14 Oct. 2002, in the Korean Intellectual Property Office.
1. Field of the Invention
The present invention relates generally to an optical disc system, and more particularly, to a method of managing shock during recording and reproduction in an optical disc system and an apparatus therefor.
2. Description of the Related Art
An optical disc system is used to record data on an optical disc, such as a compact disc (CD), a digital video disc, or a digital versatile disc (DVD) and to play the recorded data. The optical disc recording/playing apparatus records data with an optical pick-up device that generates a pit in a track of the optical disc by applying a record laser beam to the track. Spaces between pits in the track are called lands, and the pits and lands represent 0's and 1's, e.g., bits of the recorded data. The optical disc recording/playing apparatus plays data by applying a play laser beam to the track of the optical disc to be played, determining whether the pits exist by searching for a change in the strength of reflected light and playing recorded digital data according to the determination result.
The optical disc system extracts information for tracking the track of the optical disc and focusing on a bit in the track. In general, a focus error signal and a tracking error signal are used as the tracking and the focusing information. This information is used as feedback to the optical disc system to improve the tracking and focusing.
When an internal or external shock interrupts recording or playing of data, a temporary stop in recording or playing of the data before operations resume will protect existing data and preserve the disc.
In the conventional art, Japanese Laid-Open Patent Publication Hei No. 11-120680, discloses changing a recording or playing state of an optical disc system when an external shock is detected. In the 11-120690 Publication, if the strength of the detected external shock exceeds a predetermined level, an operation state of a servo is changed to stop recording or playing of data.
In the conventional art, applicant is not aware of any method of stopping and resuming recording to the optical disc when there exists external shock. In addition, there are limitations to methods of detecting the external shock by a tracking signal output from the optical pick-up.
Accordingly, an optical disc system which is capable of detecting an external shock, temporarily stopping recording or playing of data in response to the detected shock and resuming the recording or playing of data by using information stored when the recording or playing is stopped is needed to enhance the recording or playing of data in the optical disc system.
FIG. 1 shows a waveform of several signals of the optical disc system, including a summing signal of a side beam (SBAD) and a tracking signal (TRS) responding to an external shock. The SBAD, a sum of side beams of a photo diode of the optical pick-up, is used to check a focus state of an optical pick-up unit.
A level of the SBAD is sharply lowered when the external shock is applied, and a level of the TRS is sharply heightened when the shock is applied. That is, the levels are different from those in a normal state. As shown in FIG. 1, the SBAD responds to shock faster than the TRS by 120 ms.
Although the responding speed of the SBAD, i.e., a focus related signal, is faster than the TRS, the TRS is generally used to detect the shock in the conventional optical disc systems. This is because the optical disc system stops recording and does not resume recording when shock is applied.
Therefore, a method for resuming recording, as well as protecting data and the optical disc by stopping recording as soon as possible, when any external shock or disturbance interrupts recording, is desired.